We plan to continue our pursuit of the long-term goal to determine the biochemical identity of TFd, delineate its mechanism of action and its relation to lymphokine production IN VITRO and IN VIVO. This aim can be best accomplished by our continued development and exploration of meaningful, reproducible IN VITRO assays of TFd activity and/or IN VIVO transfers of DTH from human to animal or in appropriate animal to animal models. Hence we propose to explore promising leads of work that is already in progress in this laboratory. These are discussed in the Detailed Progress Report and include: 1) Studies on TFdm IN VITRO as it affects various facets of the correlates of CMI, such as Lymphocyte Blastogenesis; Lymphokine Production (MIF, LIF, LTF, CIF, IF); E-Rosette Receptor sites; Macrophage Activation; and Target-cell death; 2) Continue efforts to produce antibody and develop a Radioimmunoassay for TFd; 3) Continue studies on the IN VIVO effects of human TFd on selected immune functions in inbred normal and Nu/ Nu mice and evaluate transfer of DTH and CMI from human to mouse and mouse to mouse with TFd; 4) Continue efforts to separate biochemically and functionally the specific effects of TFd from the non-specific contributions of other immunologically active molecules present in raw dialyzates; 5) Continue efforts to replicate TFd IN VITRO in short-term and long-term human lymphocyte cultures.